The present invention relates to filter cartridges and more particularly to filter cartridges adapted for containing a particulate filter medium through which a fluid is passed for removal of selected solid and/or liquid components.
Filters of the type contemplated by the present invention have commonly been employed for filtering fluids including liquids such as water where it is desirable to remove various components from an influent source of water in order to produce an effluent particularly suited for one purpose or another. For example, such filters are commonly employed in the softening of water where mineral impurities are removed by passing the water through a bed of ion exchange resins. Similarly, water and other liquids may be passed through a particulate filter medium such as activated carbon for removing various components which are undesirable, for example, because of undesirable tastes and odors in the water.
As is also well known in the prior art, such filter cartridges are adapted for in-line use where the filter is connected with a source of fluid to be filtered, the fluid passing through the filter medium of the cartridge into a suitable outlet. In other instances, the cartridge is employed in a housing forming inlet and outlet means for communicating influent to the filter and for receiving effluent from the filter cartridge in suitably filtered form. Where the filter cartridge is adapted for use in such a housing, the cartridge is commonly contemplated for replaceable use with the housing being a generally permanent part of an in-line arrangement.
In filter operations of the type referred to above, the filter cartridge is commonly formed with a tubular outer wall element and closures at either end. The filter element is provided with foraminous or permeable material in one or more of its components for forming inlet and outlet means by which fluid is caused to pass through a particulate filter medium contained within the cartridge. Preferably, within a cartridge of the type referred to above, the end closures are of foraminous or porous construction for allowing the fluid to enter into and exit from the cartridge while passing through the particulate filter medium.
Where the filter cartridge is of a type adapted for containing a particulate filter medium through which fluid passes for carrying out the filter operation, a common problem arises in assuring uniform flow of the fluid through the particulate medium. Uniform flow is necessary in order to assure proper contact of the fluid with the particulate filter medium and removal of undesirable components to pre-established limits. However, particularly where the fluid is caused to flow through the filter cartridge under pressure, the passage of fluid through the particulate filter medium over a period of time tends to result in cavitation or channeling with relatively open passages being formed through the filter medium. In such an event, the fluid is permitted to pass through the filter medium without uniformly contacting the filter medium as required for optimum filter results.
Numerous designs for filter cartridges have been provided in the prior art in an attempt to overcome these problems in connection with maintaining proper compaction and uniform flow distribution in particulate filter mediums. In this regard, it is generally understood that a particulate filter medium may experience compaction, relative packing or even some loss of particulate filter medium permitting the development of channeling or cavitation as discussed above. Accordingly, one approach contemplated by the prior art has been the employment of means within such filter cartridges having a tendency for continually compacting the particulate filter medium in order to prevent such problems. For example, U.S. Pat. No. 3,254,771 issued June 7, 1966 disclosed a filter assembly of the type contemplated by the present invention wherein a relatively complex spring mechanism was employed within a construction including a tubular outer wall housing, end closures and various other components, the spring mechanism being adapted for initiating and maintaining a compacting force upon the filter medium in order to prevent or minimize channeling or cavitation effects within the filter medium itself.
However, all of these prior art designs adapted for eliminating or minimizing the effects of channeling, cavitation and the like have been characterized either by relatively complex filter assembly construction or other problems.
Accordingly, there has been found to remain a need for an improved filter cartridge adapted for use with particulate filter medium through which fluid is passed for carrying out a filter operation. As noted above, a particular area of improvement contemplated by the present invention lies in the need for preventing channeling or cavitation from occurring within the particulate filter medium.